Two-way vibratory feeders or conveyors have substantial applications in a variety of fields. One typical application is in foundry operations. For example, castings may be delivered to the conveyor at a location intermediate its ends and then the conveyor energized to feed the castings to one end or the other depending upon where it is desired to locate the casting.
Conventional two-way conveyors will typically include an elongated bed with an upwardly facing, generally horizontal, elongated feeding surface. The bed will conventionally be supported on isolation springs adjacent to ends. Two vibration inducing assemblies, which typically will be electric motors with eccentric weights on their output shafts, are secured to the bed generally centrally thereof. Slats at approximately a 45 degree angle connect each of the motors to the bed, with the left most motor slats being canted approximately 45 degrees to the left and the right most motor slats being canted approximately 45 degrees toward the right, and angularly separated from the left most motor slats by approximately 90 degrees.
In operation, when the left most motor is energized, vibration resulting from eccentric revolution of the associated weight will cause material to be conveyed from right to left. When the other motor is energized, conveying will occur in the opposite direction.
In many applications, it will not be unusual that there is a considerable disparity between the amount of use of the left most motor and the right most motor. If one is energized to the substantial exclusion for the other, so called "false Brinnelling" of the motor bearings in the nonenergized system will occur as a result of the vibration imparted to the bed. Lubricant may be squeezed out of the bearings as a result and when the infrequently used system is finally energized, it may fail relatively quickly as a result of bearing failure due to the false Brinnelling and the resulting insufficient lubrication.
Moreover, in foundry applications, it will be necessary that the bed be formed of metal to stand up to the continued pounding of castings. In a prior art system such as described above, vertical acceleration of the conveying surface during operation will typically exceed that of gravity. As a result, after the surface has reached its highest point of movement in a cycle of vibration, it will then be accelerated downwardly more rapidly than a casting or the like that is being conveyed on the conveying surface. The casting will temporarily separate from the conveying surface but will eventually collide with the same as movement of the conveying surface is slowed and begins to reverse while the casting is being moved downwardly under the influence of gravity. The result is a noise producing impact of the casting upon the metal of which the conveying surfaces formed, and the level of the sound will typically be undesirably high.
Moreover, in such a device, the provision of two distinct vibration inducing systems where only one is used at any given time adds considerably to the cost of the apparatus.
To avoid certain of these difficulties, Schrader, in his U.S. Pat. No. 3,746,149 issued Jul. 17, 1973, and entitled "Reversible Vibratory Feeder," proposes a system whereby a single motor may be utilized to impart vibration to a conveying surface so that it may convey in either of two directions. To achieve conveying direction reversal, in addition to the usual isolation springs, the conveying surface of Schrader is mounted on a series of air springs and as illustrated, a minimum of eight such air springs are required, four at each end of the conveying surface.
At each end of the conveying surface, two of the air springs are opposed to one another at a 45 degree angle and the other two air springs are opposed to one another at 90 degrees to the first set. The opposed air springs of one pair are pressurized to the same degree by common plumbing connections and pressure regulators are employed to achieve the desired spring rate. Conveying in one direction or the other is achieved by tuning the system to resonance with the drive by adjustment of the pressure within the air springs to limit vibratory motion to a path that is inclined upwardly and to either the right or the left.
The difficulty with this system is in its complexity in terms of requiring a number of air springs and the need to achieve tuning and pressure regulation within the systems embodying the same. Moreover, the use of a significant number of air springs and their related plumbing adds considerably to the cost of the apparatus.
To avoid these and other problems, in the commonly assigned application of Albert Musschoot, Ser. No. 08/568,018, filed Dec. 6, 1995 and entitled "Two-Way Vibratory Feeder or Conveyor," now U.S. Pat. No. 5,713,457, there is proposed a bidirectional conveying system wherein a single reversible electric motor is utilized to impart vibration to a conveying surface. The direction of conveying can be altered simply by reversing the direction of rotation of the electric motor.
In this particular device, which works well for its intended purpose, the vibration inducing system including the electric motor with eccentric weights on its output shaft, produces vibrations in sizable amplitudes in all directions. Dampers are utilized to eliminate most of the vertical vibratory force component applied to the conveying surface by the single, reversible vibration inducing system, while allowing the full amplitude of the horizonal component of such force to be applied to the bed to achieve the desired conveying effect. In this system, it is necessary that a relatively large motor be employed to achieve the desired amplitude. As the desired amplitude, at least in the vertical direction is absorbed as unnecessary to conveying and, in fact, must be absorbed in order to achieve conveying, it would seem as though a smaller motor could be used. However, when a smaller motor is employed, there is insufficient amplitude of vibratory forces in the horizonal direction to achieve the desired conveying rate. Thus, it is necessary to retain the relatively large motor, and that adds to the expense of the apparatus.
The present invention is directed to overcoming one or more of the above problems.